In this paper, we calculate the number of points on elliptic curves $E^{a^3}_0:y^2=x^3+a^3$ over ${mathbb{F}}_p$ mod 24 and $E^b_0:y^2=x^3+b$ over ${mathbb{F}}_p$ mod 6, where b is cubic non-residue in ${mathbb{F}}^*_p$. For example, if p ${equiv}$ 1 (mod 12) is a prime, and a and a(2t - 3) are quadratic residues modulo p with $3t^2{equiv}1$ (mod p), then the number of points in $E^{a^3}_0:y^2=x^3+a^3$ is congruent to 0 modulo 24.